Vitamin D (calciferol) and vitamin K2 (menaquinone) are essential nutrients supporting several aspects of health. Vitamin D is beneficial for bone and heart health and inflammation. Vitamin K2 is useful in bone, blood, and heart health.

Vitamin D is present in certain foods and can also be obtained from sun exposure. Vitamin K2 is found in certain foods and is naturally made by bacteria in the gut. Both vitamins are available in supplement form to help increase levels.

Based on your individual needs, your healthcare provider may recommend you take supplements for both vitamins D and K2.

Vitamin D is a fat-soluble vitamin naturally found in certain foods and available as a dietary supplement. Some food products are also fortified with vitamin D to increase intake.

Foods high in vitamin D include fatty fish (e.g., trout, salmon, tuna), fish liver oils, and fortified dairy products. Vitamin D can also be obtained through the skin by direct sunlight.

Vitamin D can help prevent and treat many health conditions. Some of the potential benefits of vitamin D supplements include:

• Supports bone health: Vitamin D (along with calcium) helps build and repair bones. This is especially helpful in people with osteoporosis (a condition causing brittle bones) or who are older. Most data shows that supplementation with both vitamin D and calcium provides the most bone health benefits.
• May help prevent cancer: Some studies suggest vitamin D may help prevent cancer development and slow the growth of cancer cells, particularly in breast, colorectal, prostate, and pancreatic cancer. Data is conflicting on whether vitamin D is beneficial in cancer, and more research is necessary.
• Protects heart health: High vitamin D levels have been associated with lower cardiovascular (heart and blood vessel) disease risk. This is likely due to vitamin D’s role in inflammation and the renin-angiotensin-aldosterone system (RAAS). RAAS helps regulate blood pressure and electrolyte levels. Study results are mixed, with some showing obvious benefits and others not finding much risk reduction.
• Supports mental health: Vitamin D is involved in several brain processes, and there is an association between low vitamin D levels and depression. However, studies have conflicting results on whether vitamin D supplementation helps prevent or treat depression.

More research is needed to understand the benefits of vitamin D in these and other health conditions.

Vitamin K2 is a specific type of vitamin K, a fat-soluble vitamin that contributes to several body functions. There are 10 types of vitamin K2, ranging from MK-4 through MK-13.

Vitamin K2 subtypes MK-4, MK-7, and MK-9 are the most popular and well-studied. The vitamin is found in certain animal products and fermented foods, and it’s made naturally by bacteria in the gut.

Taking vitamin K2 supplements has been shown to help with multiple health conditions. Benefits include:

• Supports bone health: Vitamin K2 aids bone growth and strength. When taken long-term, vitamin K2 may reduce the number of bone fractures and improve bone health in people with osteoporosis.
• Protects heart health: When calcium builds up in a blood vessel, the vessel hardens, making it difficult for blood to flow. This can lead to serious health conditions, like kidney disease and high blood pressure. Taking vitamin K2 can help prevent this buildup by removing calcium from the blood vessels.
• Supports blood clotting: Vitamin K2 creates the enzyme carboxylase, which is essential for maintaining normal blood clotting. If your blood is too thin and doesn’t clot well, you may be at risk for excessive bleeding or bruising. If your blood is too thick and clots too easily, it won’t flow properly through the body. This may lead to serious issues, like stroke, heart attack, or death.
• May help prevent cancer: Some research has found that vitamin K2 may block the growth of cancer cells, specifically in liver, lung, and pancreatic cancer. Other research shows that vitamin K2 may lower the risk of death caused by cancer but not the risk of getting cancer.

More research is needed to understand the benefits of vitamin K2 in these and other health conditions.

Taking vitamins D and K2 together may benefit people with certain health conditions, especially heart and bone health. One study suggests that combining vitamins K and D improves the overall strength of bones (bone mineral density).

Some researchers have hypothesized that taking both supplements together may be more effective than taking either alone for bone and heart health. More research is needed to understand how well the two supplements work together to improve and maintain bone and heart health.

Vitamin D is available as a capsule, pill, powder, or liquid and taken by mouth or prescribed as an injection for higher doses. Vitamin K2 products are available as a capsule or soft gel and taken by mouth.

Both vitamins are available as a single product or in combination with other supplements. Combination vitamin D and K2 supplements are also available. Depending on how a product is being marketed, such as for bone or heart health, it may include additional ingredients.

Dosage

Your dosage for vitamins D and K2 and how long you should take each at that dosage depends on factors like your current levels of both, health conditions you may have, and your diet.

The recommended daily allowance for vitamin D set by the National Institutes of Health (NIH) and the Food and Nutrition Board varies based on your age:

• 0-12 months: 10 micrograms (mcg), or 400 International Units (IU)
• 1-70 years: 15 mcg, or 600 IU
• 71+ years: 20 mcg, or 800 IU

The daily recommendations set by the NIH and Food and Nutrition Board for vitamin K are based on all types of vitamin K, not specifically vitamin K2. The recommended daily intakes for vitamin K are:

• Birth to 6 months: 2 micrograms
• 7-12 months: 2.5 mcg
• 1-3 years: 30 mcg
• 4-8 years: 55 mcg
• 9-13 years: 60 mcg
• 14-17 years: 75 mcg
• 19+ years: 120 mcg for men and 90 mcg for women

The amount of vitamin K2 in a supplement depends on the product. For example, the recommended dosing for vitamin K2 subtype MK-7 is usually 50-120 micrograms a day but can range from 5-600 micrograms. MK-7 doses of 180-360 micrograms a day have shown heart health benefits.

Talk with your healthcare provider or pharmacist about which type of vitamin D and vitamin K2 supplement and dosage may be best for you.

It appears safe to take vitamins D and K2 together. There is no reason to suspect abnormal effects when combining the supplements at a safe dosage.

The supplements may interact with certain medications and have some side effects, even when taken at regular doses. Talk with your healthcare provider about all risks and benefits before starting either vitamin.

Potential Drug Interactions

Vitamins D and K2 may interact with medications you are already taking.

Examples of medications that vitamin D may interact with include:

• Statin (cholesterol) medicines: Vitamin D may lower the absorption of statin drugs used to treat high cholesterol. Examples of statins include Lipitor (atorvastatin), lovastatin, and Crestor (simvastatin). Studies show this interaction does not drastically affect cholesterol levels.
• Thiazide diuretics: Taking vitamin D and thiazide diuretics (like hydrochlorothiazide) can lead to high calcium levels. This is especially significant for people with compromised renal function and older adults.
• Orlistat: Available over the counter (Alli) or as a prescription (Xenical), orlistat is a drug used for weight loss. Orlistat can lower the absorption of vitamin D in your body.

Vitamin K2 supplements may interact with medications such as:

• Warfarin: This blood thinner (brand name Coumadin) cancels out the blood clotting activity of all vitamin K types, including vitamin K2. Any sudden changes in vitamin K intake can increase or decrease the blood clotting effects of warfarin. This means your blood may become thicker or thinner, which may cause serious health issues.
• Antibiotics: These medications can change gut bacteria that make vitamin K2, potentially lowering the level of vitamin K2 in your body. This interaction is most noticeable with a group of antibiotics called cephalosporins, which include Keflex (cephalexin) and Omnicef (cefdinir). If you take antibiotics for over 10 days and have a low vitamin K2 intake, your healthcare provider may recommend a vitamin K2 supplement.
• Bile acid sequestrants: Bile acid sequestrants help lower cholesterol levels. Examples include Prevalite (cholestyramine), Colestid (colestipol), and Welchol (colesevelam). These medications may lower the absorption of vitamin K2 in your body.
• Orlistat: Orlistat can lower the absorption of vitamin K2 in your body.

Check with your healthcare provider or pharmacist about any interactions vitamins D and K2 may have with other medications or supplements you are already taking.

The tolerable upper limit for vitamin D in adults is 100 micrograms (4,000 IU). Taking amounts above this may be harmful. High levels of vitamin D in the body can lead to dangerously high calcium levels, causing dehydration, vomiting, pain, and psychological disturbances. Dangerously high vitamin D levels can also cause kidney failure, blood vessel calcifications, and abnormal heartbeats.

Vitamin K2 has not been shown to cause harm or toxicity. Maximum upper levels or doses of vitamin K2 have not been established. Taking high doses of vitamin K2 is unlikely to cause adverse health effects. Doses of vitamin K2 up to 45 milligrams (45,000 micrograms) have safely been used in studies for up to two years.

Potential side effects of vitamin D include high blood pressure, elevated calcium levels, dry mouth, sensitivity to light, and kidney impairment. These side effects are usually only seen with excessively high doses of vitamin D.

The most common side effects reported for vitamin K are gastrointestinal issues like diarrhea, nausea, or upset stomach. Skin rash may also occur with vitamin K2, and it should improve after stopping the supplement.

Vitamins D and K2 are nutrients involved in many body processes. Taking the two supplements together may benefit bone and heart health. Taking both supplements appears safe, with minimal risk for side effects when taken at appropriate doses.

Before starting these vitamins, discuss the potential risks and benefits with your healthcare provider. They will help you determine if the supplements are useful for your health concerns.